The "Big 4" Dementing Disorders

Alzheimer’s disease (65-70% of cases)

Dementia is a brain disorder that seriously affects a person’s ability to carry out daily activities. The most common form of dementia among older people is Alzheimer’s disease (AD), which initially involves the parts of the brain that control thought, memory, and language. Although scientists are learning more every day, right now they still do not know what causes AD, and there is no cure.

Scientists think that as many as 4.5 million Americans suffer from AD. The disease usually begins after age 60, and risk goes up with age. While younger people also may get AD, it is much less common. About 5 percent of men and women ages 65 to 74 have AD, and nearly half of those age 85 and older may have the disease. It is important to note, however, that AD is not a normal part of aging.

AD is named after Dr. Alois Alzheimer, a German doctor. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. He found abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles). Today, these plaques and tangles in the brain are considered signs of AD.

Scientists also have found other brain changes in people with AD. Nerve cells die in areas of the brain that are vital to memory and other mental abilities, and connections between nerve cells are disrupted. There also are lower levels of some of the chemicals in the brain that carry messages back and forth between nerve cells. AD may impair thinking and memory by disrupting these messages.

Dementia with Lewy bodies, the second most frequent cause of degenerative dementia in elderly adults, is a neurodegenerative disorder associated with abnormal structures (Lewy bodies) found in certain areas of the brain. Because these structures and many of the symptoms of dementia with Lewy bodies are associated with Parkinson's and Alzheimer's diseases, researchers do not yet understand whether dementia with Lewy bodies is a distinct clinical entity or perhaps a variant of Alzheimer's or Parkinson's disease.

Recent research has revealed that Lewy bodies contain deposits of a protein called alpha-synuclein that is also linked to Parkinson's disease and multiple system atrophy. Symptoms can range from traditional parkinsonian effects, such as loss of spontaneous movement (bradykinesia), rigidity (muscles feel stiff and resist movement), tremor, and shuffling gait, to effects similar to those of Alzheimer's disease, such as acute confusion, loss of memory, and loss of, or fluctuating, cognition.

Visual hallucinations may be one of the first symptoms noted, and patients may suffer from other psychiatric disturbances such as delusions and depression. Onset of the disorder usually occurs in older adults, although younger people can be affected as well. In 1996 scientists published guidelines for the diagnosis of dementia with Lewy bodies (McKeith IG, et al, Neurology, vol 47, pp 1113-1114, Nov 1996).

Frontotemporal dementia (FTD) describes a clinical syndrome associated with shrinking of the frontal and temporal anterior lobes of the brain. Originally known as Pick’s disease, the name and classification of FTD has been a topic of discussion for over a century. The current designation of the syndrome groups together Pick’s disease, primary progressive aphasia, and semantic dementia as FTD. Some doctors propose adding corticobasal degeneration and progressive supranuclear palsy to FTD and calling the group Pick Complex. These designations will continue to be debated.

As it is defined today, the symptoms of FTD fall into two clinical patterns that involve either (1) changes in behavior, or (2) problems with language. The first type features behavior that can be either impulsive (disinhibited) or bored and listless (apathetic) and includes inappropriate social behavior; lack of social tact; lack of empathy; distractability; loss of insight into the behaviors of oneself and others; an increased interest in sex; changes in food preferences; agitation or, conversely, blunted emotions; neglect of personal hygiene; repetitive or compulsive behavior, and decreased energy and motivation. The second type primarily features symptoms of language disturbance, including difficulty making or understanding speech, often in conjunction with the behavioral type’s symptoms. Spatial skills and memory remain intact. There is a strong genetic component to the disease; FTD often runs in families.

Multi-infarct dementia is the most common form of vascular dementia, and accounts for 10-20% of all cases of progressive, or gradually worsening, dementia. It usually affects people between the ages of 60-75, and is more likely to occur in men than women.

Probable risk factors are high blood pressure and advanced age. CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) is an inherited form of MID. This disease can cause stroke, dementia, migraine-like headaches, and psychiatric disturbances.

Symptoms of MID, which often develop in a stepwise manner, include confusion, problems with recent memory, wandering or getting lost in familiar places, loss of bladder or bowel control (incontinence), emotional problems such as laughing or crying inappropriately, difficulty following instructions, and problems handling money. Usually the damage is so slight that the change is noticeable only as a series of small steps. However over time, as more small vessels are blocked, there is a gradual mental decline. MID, which typically begins between the ages of 60 and 75, affects men more often than women.

Because strokes occur suddenly, loss of thinking and remembering skills - the symptoms of dementia - also occurs quickly and often in a step-wise pattern. People with multi-infarct dementia may even appear to improve for short periods of time, then decline again after having more strokes. Some of these small strokes produce no obvious symptoms and are noticed only on brain imaging studies, so they are sometimes called "silent strokes." A person may have several small strokes before noticing serious changes in memory or other signs of multi-infarct dementia.

Transient ischemic attacks, or TIAs, are caused by a temporary blockage of blood flow. Symptoms of TIAs are similar to symptoms of stroke and include mild weakness in an arm or leg, slurred speech, and dizziness. Symptoms generally do not last for more than 20 minutes. A recent history of TIAs greatly increases a person’s chance of suffering permanent brain damage from a stroke. Prompt medical attention is required to determine what may be causing the blockage in blood flow and to start proper treatment (such as aspirin or warfarin).

If you believe someone is havinga stroke - if a person experiences sudden weakness or numbness on one or both sides of the body, or difficulty speaking, seeing, or walking - call 911 immediately. If the physician believes the symptoms are caused by a blocked blood vessel, treatment with a "clot buster," such as t-PA (tissue plasminogen activator), within 3 hours can reopen the vessel and may reduce the severity of the stroke.